Cooking Appliance

ABSTRACT

A cooking appliance, particularly an elevated-mounted cooking appliance, comprising: at least one muffle, which delimits a cooking compartment and whose muffle opening is surrounded by a muffle frame; a door for closing the muffle opening; a drive device, which is controlled by a control circuit and which serves to displace the door, and; a pinching protection device for identifying a pinching instance. Once a pinching instance has been identified by the pinching protection device, the drive device can be controlled by the control circuit so that a force applied to the door does not exceed a specified force time profile.

The present invention relates to a cooking appliance, in particular a high-level cooking appliance, comprising at least a muffle which delimits a cooking compartment and has a muffle opening, a door for closing the muffle opening, a drive device which is controlled by a control circuit and is for causing the door to travel, and a pinching protection device for detecting a pinching instance.

DE 102 28 140 A1 discloses a high-level cooking appliance in which any pinching of objects at the base door can be detected by a plurality of pinching protection switches between the base door and the muffle compartment, wherein said pinching protection switches can be actuated independently of one another. In this case it is additionally possible to analyze a pressure increase in a door seal having a hollow profile.

DE 101 64 239 A1 describes a pinching protection which is triggered by different tensile forces at the traction cables which drive the base door. A torque sensor is also described which measures a load torque exerted on the drive shaft of the electric motor. Tensile force sensors, piezoelectric sensors and deformation or stress/strain sensors are also listed as sensors.

In addition, DE 102 28 141 A1 describes an optoelectronic sensor for detecting a pinching instance, wherein said sensor switches according to the quantity of reflected light.

Countermeasures such as stopping or reversing the door are introduced upon detection of the pinching instance. There is typically a perceptible time period which elapses between the detection of the pinching instance and the coming into effect of the countermeasures due to the inertia of the system; thus, for example, the motor must be stopped and restarted for the purpose of reversing.

It is disadvantageous that the above-described pinching detection systems do not provide measures for the time between the detection of the pinching instance and the subsequent countermeasure. Likewise, no measures are provided for identifying malfunctions of the pinching protection.

The present invention therefore addresses the problem of providing improved operational safety for the pinching instance on a cooking appliance of the type described above.

The present problem is solved by the cooking appliance having the features recited in claim 1 and a method in accordance with claim 17.

For this, the cooking appliance, which is in particular a high-level cooking appliance but can also be a cooking appliance having a baking carriage, is configured in such a way that, after a pinching instance has been detected by the pinching protection device, the control circuit regulates the drive device such that a force which is applied to the door does not exceed a specific force/time profile.

The pinching protection is preferably not embodied as a discrete assembly, but is functionally integrated in the control circuit or its module(s), which typically already includes a microcontroller.

For improved safety coordination it is advantageous if a first force/time profile is provided for a pinching instance in the closing direction of the door, i.e. as a result of upward travel in the case of a high-level cooking appliance. An object is typically pinched between base door and muffle frame or housing in this case. Alternatively or additionally, a second force/time profile can be provided for a pinching instance in the opening direction of the door, if an object is then typically pinched between base door and work surface in the case of a high-level cooking appliance.

The first force/time profile, i.e. in a closing direction, advantageously has a first section having a maximum force F=100 N for 5 s, followed by a second section having a maximum force F=25 N. The third section can also be reduced further to 0 N after a certain time.

The second force/time profile advantageously has a first section having a maximum force F=400 N for 0.5 s, followed by a second section having a maximum force F=150 N for 4.5 s, followed by a third section having a maximum force F=25 N. The third section can also be reduced further to 0 N after a certain time.

In order to react quickly and with minimal errors to a pinching instance it is advantageous if the pinching instance can be detected by monitoring a travel speed of the door, e.g. on the basis of percental or absolute deviation from a reference speed value or on the basis of a high positive or negative acceleration.

Furthermore, it is advantageous if the travel movement of the door generally can be regulated depending on speed, and thus independently of a load or frictional conditions. In addition, provision is advantageously made for reaching a reference speed via speed ramps.

For greater safety, it is advantageous if the travel direction of the door is reversed in the pinching instance, in particular if a pinching protection can only be activated when a reference speed of the door has been reached. It is also advantageous if the force/time profile can only be activated if a reference speed of the door has been reached.

In addition, provision is advantageously made for at least one stop switch which is arranged in the region between muffle opening and door, wherein an actuation of the at least one stop switch deactivates the pinching protection device. It is then advantageous if the at least one stop switch can be actuated within an opening distance of 4 mm between muffle frame and base door. In the event that the at least one stop switch is actuated, it is then advantageous if the door can be pushed onto the muffle opening using a defined force.

In particular, the invention is suitable for high-level cooking appliances in which the muffle opening is a base-side muffle opening and the door is a base door which preferably moves in a linear manner.

The invention is described in greater detail below with reference to the appended schematic figures, in which:

FIG. 1 shows a perspective view of a high-level cooking appliance which is mounted on a wall and has a lowered base door;

FIG. 2 shows a perspective view of the high-level cooking appliance with closed base door;

FIG. 3 shows a perspective view of a housing of the high-level cooking appliance without the base door;

FIG. 4 shows a schematic side view, in cross section along the line I-I from FIG. 1, of the high-level cooking appliance which is mounted on a wall and has a lowered base door;

FIG. 5 shows a front view of a further embodiment of a high-level cooking appliance;

FIG. 6 to 11 show diagrams of travel movements of a base door in the context of various limiting conditions;

FIGS. 12 and 13 show force/time profile curves for a base door.

FIG. 1 shows a high-level cooking appliance with a housing 1. The rear side of the housing 1 is mounted on a wall 2 in the manner of a suspended cabinet. A cooking compartment 3, which can be monitored via a viewing window 4 installed in the front side of the housing 1, is defined in the housing 1. It can be seen from FIG. 4 that the cooking compartment 3 is delimited by a muffle 5 which is equipped with a heat-insulating jacket (not shown) and that the muffle 5 has a base-side muffle opening 6. The muffle opening 6 can be closed by means of a base door 7. The base door 7 is shown lowered in FIG. 1, wherein its underside is in contact with a work surface 8 of a kitchen entity. In order to close the cooking compartment 3, the base door 7 must be repositioned to the position shown in FIG. 2, the so-called “zero position”. For the purpose of repositioning the base door 7, the high-level cooking appliance has a drive device 9, 10. The drive device 9, 10 has a drive motor 9 which is illustrated by means of broken lines in FIGS. 1, 2 and 4 and is arranged between the muffle 5 and an external wall of the housing 1. The drive motor 9 is arranged in the region of the rear side of the housing 1 and, as shown in FIG. 1 or 4, has an active connection to a pair of lifting elements 10 which are connected to the base door 7. In this case, as shown in the schematic side view in FIG. 4, each lifting element 10 is designed in the form of an L-shaped carrier whose vertical limb extends from the drive motor 9 in the housing. For the purpose of repositioning the base door 7, the drive motor 9 can be actuated with the aid of an operating panel 12, which is arranged on the front of the base door 7 in accordance with FIGS. 1 and 2, and a control circuit 13. As shown in FIG. 4, the control circuit 13 is located behind the operating panel 12 within the base door 7. The control circuit 13, which is composed of a plurality of spatially and functionally separate printed circuit boards that communicate via a communication bus, represents a central control unit for the appliance operation and controls and/or adjusts e.g. heating, travel of the base door 3, conversion of user inputs, lighting, pinching protection, timing of heating elements 16, 17, 18, 22 and much more.

It can be seen from FIG. 1 that a top side of the base door 7 has a cooking matrix 15. Almost the entire surface of the cooking matrix 15 is occupied by heating elements 16, 17, 18, these being indicated in FIG. 1 by dash-dotted lines. In FIG. 1, the heating elements 16, 17 are two separate cooking position heating elements of different sizes, while the heating element 18 is a surface heating element which is provided between the two cooking position heating elements 16, 17 and almost surrounds the cooking position heating elements 16, 17. The cooking position heating elements 16, 17 define associated cooking zones or cooking rings for the user; the cooking position heating elements 16, 17 and the surface heating element 18 together define an underside-heating zone. The zones can be indicated by means of a suitable motif on the surface. The heating elements 16, 17, 18 can be controlled in each case via the control circuit 13.

In the exemplary embodiment shown, the heating elements 16, 17, 18 are embodied as radiant heating elements which are covered by a glass ceramic plate 19. The glass ceramic plate 19 has approximately the dimensions of the top of the base door 7. The glass ceramic plate 19 is also equipped with mounting openings (not shown), through which sockets project for the purpose of holding support parts 20 for cooking item carriers 21, as is also shown in FIG. 4. Instead of a glass ceramic plate 19, it is also possible to use other—preferably quick-reacting—covers, e.g. thin sheet metal.

With the aid of an operating knob which is provided in the operating panel 12, the high-level cooking appliance can be switched to a cooking position operating mode or an underside-heating operating mode, wherein these are explained below.

In the cooking position operating mode, the cooking position heating elements 16, 17 can be controlled individually via the control circuit 13 by means of operating elements 11 which are provided in the operating panel 12, while the surface heating element 18 remains unused. The cooking position operating mode can be implemented when the base door 7 is lowered as shown in FIG. 1. However, it can also be operated in an energy-saving function when the cooking compartment 3 is closed and the base door 7 is raised.

In the underside-heating operating mode, the control device 13 controls not only the cooking position heating elements 16, 17 but also the surface heating element 18.

In order to achieve a maximally even browning impression of the cooking item during the underside-heating operation, it is critical that the cooking matrix 15 which provides the underside heating exhibits an even distribution of the heat power output over the surface of the cooking matrix 15, even though the heating elements 16, 17, 18 have different nominal powers. Therefore the heating elements 16, 17, 18 are preferably not switched to a continuous operation by the control circuit 13, but the current supply to the heating elements 16, 17, 18 is timed. In this case, the different nominal heating powers of the heating elements 16, 17, 18 are reduced individually in such a way that the heating elements 16, 17, 18 provide an equal distribution of the heating power output over the surface of the cooking matrix 15.

FIG. 4 schematically shows the position of a fan 23, e.g. for the generation of recirculating air in the case of hot air operation or for supplying fresh air. Furthermore, provision is made for a topside-heating element 22 which is attached at a top side of the muffle 5 and can be embodied as a single circuit or multiple circuit, e.g. having an inner circuit and an outer circuit. It is also possible—not shown here for the sake of greater clarity—to provide for further heating elements such as a ring heating element between a rear wall of the housing 1 and the muffle. The different operating modes including e.g. topside-heating operation, hot-air operation or rapid-heating operation can be set by the control circuit 13 by switching on and setting the heating power of the heating elements 16, 17, 18, 22 correspondingly, optionally with activation of the fan 23. The setting of the heating power can be done by means of suitable timing. In addition, the cooking matrix 15 can be embodied differently, e.g. with or without a grilling zone, as a simple heat-retention zone (featuring a single circuit or multiple circuits) without cooking rings, etc. The housing 1 has a seal 24 which faces the base door 7.

The operating panel 12 is normally arranged on the front side of the base door 7. Alternatively, other arrangements are also conceivable, e.g. on the front side of the housing 1, divided over various partial panels and/or partly on side surfaces of the cooking appliance. Further configurations are possible. The operating elements 11 are not restricted in terms of their construction, and can comprise e.g. operating knobs, tumbler switches, pushbuttons and plastic membrane buttons. The display elements 14 comprise e.g. LED, LCD and/or touchscreen displays.

FIG. 5 schematically shows a high-level cooking appliance from the front (not to scale), wherein the base door 7 is open and is in contact with the work surface 8. The closed state is drawn by means of a broken line.

In this embodiment there are two travel switch panels 25 on the front side of the permanently attached housing 1. Each travel switch panel 25 comprises two pushbuttons, specifically an upper CLOSE pushbutton 25 a which causes a base door 7 to travel upward in a closing direction, and a lower OPEN pushbutton 25 b which causes a base door 7 to travel downward in an opening direction. Without automatic operation (see below) the base door 7 only travels upward as a result of continuous simultaneous depression of the CLOSE buttons 25 a of both travel switch panels 25, if possible; the base door 7 also only travels downward as a result of continuous simultaneous depression of the OPEN buttons 25 b of both travel switch panels 25, if possible (manual operation). Since increased operating alertness on the part of the user is assumed in the case of manual operation, and both hands are also used here, pinching protection is only optional. In the case of an alternative embodiment, travel switch panels 26 are attached on opposite external sides of the housing 1 and have corresponding CLOSE buttons 26 a and OPEN buttons 26 b, as drawn using dotted lines.

The control circuit 13, which is drawn using dash-dotted lines and is located in the interior of the base door 7 behind the operating panel 12, switches the drive motor 9 in such a way that the base door 7 begins to move gently, i.e. not abruptly by simply starting the drive motor 9, but via a defined ramp.

In this exemplary embodiment, the control circuit 13 comprises a memory unit 27 for storing at least a destination or travel position P0, P1, P2, PZ of the base door 7, preferably using volatile memory modules, e.g. DRAMs. If a destination position P0, P1, P2, PZ is stored, following actuation of one of the buttons 25 a, 25 b or 26 a, 26 b of the travel switch panels 25 or 26, the base door can travel independently in the selected direction until the next destination position has been reached or until one of the buttons 25 a, 25 b or 26 a, 26 b is actuated again (automatic operation). In this exemplary embodiment, the lowermost destination position PZ corresponds to the maximum opening, the (zero) position P0 corresponds to the closed state, and P1 and P2 are freely selectable intermediate positions. If the last destination position for a direction has been reached, manual operation is additionally necessary for further travel, if possible (i.e. if the last final positions do not correspond to a maximally open final state or to the closed final state). Similarly, if no destination position is stored for a direction (which would be the case e.g. for an upward movement into the closed position if only PZ is stored but not P0, P1, P2), movement in this direction requires manual operation. If no destination position is stored, e.g. in the case of a new installation or following a power disconnection, no automatic operation is possible. If the base door 7 is to travel using the automatic operation, pinching protection is preferably activated.

Automatic operation and manual operation are not mutually exclusive: as a result of continuous actuation of the travel switch panel(s) 25, 26, the base door 7 also moves in manual operation if a destination position is nonetheless available in this direction. In this case, it is possible to define e.g. a maximum actuation time of the travel panels 25 or 26, or of the associated buttons 25 a, 25 b and 26 a, 26 b respectively, for the purpose of activating the automatic operation, e.g. 0.4 seconds.

A destination position P0, P1, P2, PZ can be any desired position of the base door 7 between and including the zero position P0 and the maximum opening position PZ. However, the maximum stored opening position PZ does not have to be the position which is in contact with the work surface 8. Storage of the destination position P0, P1, P2, PZ can be carried out with the base door 7 at the desired destination position P0, P1, P2, PZ by means of e.g. actuating a confirmation button 28 in the operating panel 12 for several seconds (e.g. two seconds). For the sake of greater clarity, available optical and/or acoustic signal emitters which output corresponding signals following storage of a destination position are not drawn. Arriving at the desired destination position P0, P1, P2, PZ to be set is achieved e.g. by means of—in this exemplary embodiment—two-handed operation of the travel switch panels 25 or 26 and manual travel to this position:

It is possible to store just one or, as shown in this exemplary embodiment, also a plurality of destination positions P0, P1, P2, PZ in the memory unit 27. In the case of a plurality of destination positions P0, P1, P2, PZ, these can be reached successively by actuating the corresponding travel buttons 25 a, 25 b or 26 a, 26 b.

By virtue of a plurality of destination positions P0, P1, P2, PZ, the high-level cooking appliance can easily be adjusted to the desired operating height of a plurality of users. The destination position(s) can advantageously be deleted and/or overwritten. In one embodiment, for example, only one destination position in the open state can be stored, while the zero position P0 is detected automatically and can be reached automatically. Alternatively, the zero position P0 must also be stored in order that it can be reached automatically.

For ergonomic use, it is particularly advantageous if the or a destination position P1, P2, PZ opens the base door 7 at least approximately 400 mm to approximately 540 mm (i.e. P1-P0, P2-P0, PZ-P0>=40 cm to 54 cm). At this opening distance, the cooking item carriers 21 can easily be inserted into the support parts 20. In this case, it is advantageous if the viewing window 4 is mounted at approximately eye level of the user or somewhat lower, e.g. by means of a template which indicates the dimensions of the cooking appliance.

A power failure protection for bridging power failures of approximately 1 to 3 s, preferably up to 1.5 s, is present but not illustrated.

The drive motor 9 from FIG. 1 has at least one sensor unit 31, 32 on a motor shaft 30, these being arranged before or after a transmission if applicable, in order to measure a travel displacement or a position and/or a speed of the base door 7. The sensor unit can comprise e.g. one or more induction sensors, Hall-effect sensors, optoelectronic sensors, SAW sensors, etc. In this case, in order to measure displacement and speed in a simple manner, two Hall-effect (partial) elements 31 are attached to the motor shaft 30 such that they are offset by 180°—i.e. opposite each other—and a Hall-effect measurement pick-up 32 is separately attached in a fixed manner in this region of the motor shaft. When a Hall-effect element 31 then travels past the measurement pick-up 32 as the motor shaft 30 rotates, a measurement signal or sensor signal is generated which is closely approximate to digital. Using (not necessarily) two Hall-effect elements 31, therefore, two signals are output with one rotation of the motor shaft 30. By analyzing these signals relative to time, e.g. their time difference, it is possible to determine the speed vL of the base door 7, e.g. using comparison tables or a real-time conversion in the control circuit 13. By means of adding or subtracting the measurement signals, it is possible to determine a travel displacement or a position of the base door 7.

A speed regulator can realize the speed e.g. via a PWM-controlled power semiconductor.

In order to determine the zero point, the displacement measurement is automatically reset by initializing in the zero position P0 of the base door 7 at each start-up, in order that e.g. an erroneous sensor signal output or sensor signal pick-up is not perpetuated.

The drive motor 9 can be operated by actuating both travel switch panels 25 or 26 even if the main switch 29 is switched off.

Instead of two separate switches per travel panel 25, 26, a single switch per travel panel is also possible, e.g. a tumbler switch which has a neutral position and only switches under pressure. Other forms are also possible. The type and arrangement of the operating elements 28, 29 of the operating panel 12 are likewise not restricted.

The arrangement and distribution of the control circuit 13 is flexible and not restricted in this case, and can therefore comprise a plurality of boards, e.g. a display board, a control board and a lift board, which are physically separate.

A 4-mm opening can be detected by stop switches 33 which, when actuated, deactivate a pinching protection.

The high-level cooking appliance can also be embodied without a memory unit 27, in which case no automatic operation is then possible. This can be suitable for increased operating safety, e.g. as protection against pinching.

FIG. 6 shows a diagram (not to scale) which plots the travel speed vL of the base door 7 in mm/s relative to the position of the base door in mm from the zero position P0 for a travel of the base door 7 from the closed state where P0=0 mm to PZ=maximum opening at 530 mm here using the manual travel operation (i.e. without automatic travel) and, as indicated by the dotted arrow, a halt of the travel movement between P0 and PZ. The curve runs in the direction of the arrow, i.e. from right to left. The arrows that are present above the curve and point downward indicate actuations of the operating panel 12.

The travel movement of the base door 7 downward begins with two-handed actuation of the travel switch panels 25, 26 or the OPEN switches 25 b or 26 b as indicated by the upper left-hand vertical arrow. The control circuit 13 regulates the drive motor 9 in such a way that the base door 7 gently, i.e. via a defined ramp R1, reaches its reference speed of vL=50 mm/s in this case. The ramp R1 is linear here. The drive motor 9 is not simply switched on, therefore.

As a result, the travel movement is also load-independent, in particular it is independent of the load of the base door 7 or changed frictional conditions of the mechanism. An input variable for this can be the rotational speed of the drive motor 9, which speed can be measured e.g. by Hall-effect sensors.

After reaching the reference speed of vL=50 mm/s, the base door 7 travels downward in a constant manner until it nears the maximum opening PZ, which is derived from the structurally predetermined maximum travel of the base door 7 or as a result of reaching the work surface 8. In this figure, it is assumed that the structural maximum opening PZ is reached. In this case, the control circuit 13 detects this approach and automatically brakes the base door 7 gently, i.e. using a defined ramp R2, to arrive at PZ. Both ramps R1 and R2 can have different gradients or shapes. The arrival at the base plate can be detected by stop switches 33 and/or by monitoring the travel displacement.

If one or both of the travel switches 25 b, 26 b is triggered, as indicated by the upper left-hand vertical arrow, the base door 7 stops abruptly without a ramp, as indicated by the dotted arrow. In this mode, starting takes place in a gentle manner, but—unless the final position is reached—stopping takes place abruptly.

The cooking compartment 3 is not opened, i.e. the base door 7 is not moved from the zero position P0, if an opening safety device is active, e.g. if a specific temperature is exceeded in the cooking compartment, e.g. 425° C. or 600° F., or if a child safety device is activated.

FIG. 7 shows a diagram (not to scale) which is similar to FIG. 6 for travel of the base door 7 from the closed state to a stored position P1=476 mm using the automatic travel operation.

In this case, the base door 7 automatically begins to travel to the position P1 as a result of briefly actuating one of the OPEN switches 25 b or 26 b, as indicated by the upper right-hand vertical arrow. Here again, the base door 7 is gently started (right-hand ramp) and automatically braked (left-hand ramp). In this embodiment, using automatic operation it is possible to choose between two fixed reference speeds, specifically 75 mm/s (broken line) and 50 mm/s (continuous line), wherein the slower speed is advantageous for older users in particular. The slower speed level is preset, e.g. upon delivery. Provision can also be made for more than two speed levels or reference speeds; unrestricted setting of the reference speed(s) by the user is also conceivable. Also advantageous is provision for switching between at least two speed levels of 50 mm/s and 65 mm/s, e.g. upon device initialization.

FIG. 8 shows a diagram (not to scale) for travel of the base door 7 from the maximum opening position PZ to the zero position P0, i.e. to the closed state, using the manual operation.

The travel movement of the base door 7 upward begins with two-handed actuation of the CLOSE switches 25 a or 26 a, as indicated by the upper left-hand vertical arrow. The control circuit 13 regulates the drive motor 9 in such a way that the base door 7 starts gently from PZ to its reference speed of vL=50 mm/s, and then travels constantly at this reference speed (rightward).

The control circuit 13 detects an approach at the zero position P0 and gently brakes the base door 7 at the correct time in advance. Instead of now coming to a halt via the linear ramp directly at the zero position P0, however, 4 mm before the zero position P0 provision is made for switching from speed-dependent voltage to defined voltage, i.e. by supplying a corresponding voltage to the motor 9. It is thus possible to set a maximum force development as a result of inhibiting the drive motor 9. This voltage varies depending on the previous history of the procedure (load, frictional conditions, etc.). The detection of the 4-mm opening distance is done via the displacement measurement or additionally or alternatively via the stop switches 33. In the region from P0 to P0+4 mm, it is possible to dispense with pinching protection.

As in FIG. 6, if one or both of the travel switches 25 b, 26 b is triggered, as indicated by the upper right-hand vertical arrow, the base door 7 stops abruptly without a ramp as indicated by the dotted arrow.

FIG. 9 shows a diagram (not to scale) for travel of the base door 7 from a stored position P1=476 mm to the closed state P0 using the automatic travel operation. Unlike the manual travel operation shown in FIG. 8, only one of the CLOSE switches 25 a, 26 a need be briefly actuated, as indicated by the upper vertical arrow. The base door 7 then travels in a manner similar to FIG. 7, but in the other direction. When the zero position P0 is approached, in a similar manner to the situation in FIG. 8, the braking ramp for the last 4 mm opening changes from a state which is dependent on speed to a state which is dependent on load or closing force.

FIG. 10 shows a diagram which is similar to FIG. 8, in which pinching now occurs at a reference speed of vL=50 mm/s, as indicated by the upper vertical arrow. As a result of pinching e.g. a hand or a saucepan etc. between the base door 7 and the housing 1, the speed of the base door 7 decreases because the object obstructs further travel. The monitoring of the lifting speed takes place here e.g. by means of analyzing the sensor signals of the motor shaft, wherein e.g. the time between the measurement signals or impulses is analyzed. Only in a second instance is the motor current monitored, this being a somewhat slower method. In particular, the force which can be generated by the motor 9 for the purpose of travel is limited, in order to prevent accidents being caused by too severe pinching (see also FIGS. 12 and 13). The deviation from the reference speed is detected by the control circuit 13, e.g. as a result of a speed variation or a time-relative change of the speed. In addition, the base door reverses in order that the object can be removed; an e.g. acoustic warning signal is also output if applicable. The base door 7 only starts again subsequently if a travel button panel 25, 26 is actuated again accordingly.

In order to ensure that the pinching instance is not triggered erroneously, e.g. as a result of a changed load or a change in the running characteristics of the mechanism, firstly the pinching protection might only be activated if the base door 7 has reached its reference speed (if a travel button 25 a, 25 b, 26 a, 26 b is triggered prior to this the base door 7 halts immediately), and secondly a plurality of sensor signals might be analyzed, e.g. averaged.

FIG. 11 shows the pinching instance (upper vertical arrow) during the opening travel of the base door 7 using the automatic operation to a destination position P1, wherein an object is pinched between the underside of the base door 7 and the work surface 8. In this case, the pinching detection can take place via two redundant stop switches which detect a reduction—in particular an uneven reduction—in the loading of the base door 7, whereupon the drive motor 9 reverses. The maximum permitted force/time profile (see FIGS. 12 and 13) is not exceeded in this case.

FIG. 12 shows a force F in N, this being the maximum force which can be applied to the base door 7 in the pinching instance when traveling in a closing direction (i.e. upward), relative to the elapsed time t in s as a first force/time profile FT1.

In the pinching instance, the possible closing force is limited to 100 N, corresponding to approximately 10 kg, for 5 s when t=0 s. This is useful e.g. if the motor 9 power is increased by the control device 13 in order to maintain the reference speed. In particular, this ensures that body parts are not injured. If the base door is advanced for 5 s using (maximally) 100 N, the maximum force that can be applied decreases further to 25 N, e.g. for 5 seconds. Subsequently, this force level can be maintained or e.g. reduced further to 0 N. It must be emphasized that this force/time profile FT1 only specifies the maximum applicable force, and the actual applicable force is normally lower than this, e.g. if the pinching instance is detected by the control device 13 and the base door 7 is correspondingly reversed after t=0.5 s, whereupon the applied force drops from 100 N to e.g. 0 N.

The maximum force threshold of 100 N can also apply for other travel situations.

FIG. 13 shows a force F in N, this being the maximum force which can be applied to the base door 7 in the pinching instance when traveling in an opening direction (i.e. downward), relative to the elapsed time t in s as a second force/time profile FT2. In this case, the drive motor 9 can apply up to 400 N to the base door 7 in a first block of t=[0 s; 0.5 s], then 150 N when t=[0.5 s; 5 s], and then 25 N. Obviously, the time intervals and force thresholds of the force/time profiles FT1, FT2 can be adapted to the implementation and to further limiting conditions.

LIST OF REFERENCE SIGNS

-   1 Housing -   2 Wall -   3 Cooking compartment -   4 Viewing window -   5 Muffle -   6 Muffle opening -   7 Base door -   8 Work surface -   9 Drive motor -   10 Lifting element -   11 Operating element -   12 Operating panel -   13 Control circuit -   14 Display elements -   15 Cooking matrix -   16 Cooking position heating element -   17 Cooking position heating element -   18 Surface heating element -   19 Glass ceramic plate -   20 Support part -   21 Cooking item carrier -   22 Top heating element -   23 Fan -   24 Seal -   25 Travel switch panel -   25 a Travel switch upward -   25 b Travel switch downward -   26 Travel switch panel -   26 a Travel switch upward -   26 b Travel switch downward -   27 Memory unit -   28 Confirmation button -   29 Main switch -   30 Motor shaft -   31 Hall-effect element -   32 Measurement pick-up -   33 Stop switch -   FT1 First force/time profile -   FT2 Second force/time profile -   P0 Zero position -   P1 Intermediate position -   P2 Intermediate position -   PZ Final position -   R1 Speed ramp -   R2 Speed ramp -   vL Travel speed of the base door 

1-18. (canceled)
 19. A cooking appliance comprising: a muffle having a muffle body defining a cooking compartment with a cooking compartment access opening formed in the muffle body; a door configured for traveling movement in and out of a covering relation with the muffle access opening; a drive device in mechanical communication with the door for applying motive force thereto; a control circuit in operational communication with the drive device for controlling door motion; and a pinch protection device in operational communication with the control circuit for detecting a pinch event, wherein upon detection of a pinch event by the pinch protection device, the control circuit controls the drive device to apply a force to the door that does not exceed a predetermined force/time profile, with the force/time profile representing a predetermined force applied for a predetermined time period.
 20. The cooking appliance according to claim 18 wherein the pinch protection device is functionally integrated in the control circuit.
 21. The cooking appliance according to claim 19 wherein a first force/time profile is applied for a pinch event occurring when the door is being driven toward the muffle access opening and a second force/time profile is applied for a pinch event occurring when the door is being driven away from the muffle access opening.
 22. The cooking appliance according to claim 21 wherein the first force/time profile includes a first portion having a maximum force of 100 N for 5 s, and a second portion having a maximum force of 25 N for an indeterminate time.
 23. The cooking appliance according to claim 21 wherein the second force/time profile includes a first portion having a maximum value of 400 N for 0.5 s; a second portion having a maximum force of 150 N for 4.5 s; and a third portion having a maximum force of 25 N for an indeterminate time.
 24. The cooking appliance according to claim 19 and further comprising means for monitoring door speed including means for detecting a pinch event.
 25. The cooking appliance according to claim 24 wherein the means for detecting a pinch event includes means for determining a reference speed and means for a comparing the door speed with the reference speed to determine a deviation of the door speed from the reference speed, with a predetermined deviation being indicative of a pinch event.
 26. The cooking appliance according to claim 5 wherein the means for monitoring the door speed includes means for detecting a change of door speed within a predetermined time period with a predetermined change in door speed within a predetermined time period being indicative of a pinch event.
 27. The cooking appliance according to claim 19 the control circuit includes means for regulating door movement as a function of door speed.
 28. The cooking appliance according to claim 19 wherein the control circuit includes means for causing the drive device to reverse door movement upon detection of a pinch event by the pinch protection device.
 29. The cooking appliance according to claim 25 wherein the pinch protection device becomes operational when the means for monitoring door speed detects that door speed has reached the reference speed.
 30. The cooking appliance according to claim 25 wherein the control circuit controls the drive device according to a predetermined force/time profile when the means for monitoring door speed detects that door speed has reached the reference speed.
 31. The cooking appliance according to claim 19 and further comprising at least one stop switch operationally disposed between the muffle body and the door wherein an actuation of the at least one stop switch deactivates the pinch protection device.
 32. The cooking appliance according to claim 30 wherein the at least one stop switch becomes operational a distance of about 4 mm between the muffle body and the door.
 33. The cooking appliance according to claim 31 wherein the door can be moved into a closed relation with the access opening with a predetermined force when the at least one stop switch is actuated.
 34. The cooking appliance according to claim 19 wherein said cooking appliance is configured for mounting above countertop level with a plurality of sides and a downwardly directed muffle opening and the door is configured for covering the downwardly directed muffle opening.
 35. A method for operating a cooking appliance comprising the steps of: providing a muffle having a muffle body defining a cooking compartment with a muffle access opening formed in the muffle body; a door configured for traveling movement in and out of a covering relation with the muffle access opening; a drive device in mechanical communication with the door for applying motive force thereto; a control circuit in operational communication with the drive device for controlling door motion; and a pinch protection device in operational communication with the control circuit; detecting a pinch event using the pinch protection device; and controlling the drive device using the control circuit to apply a force to the door that does not exceed a predetermined force/time profile, with the force/time profile representing a predetermined force applied for a predetermined time period. 